My brother says that “If space is expanding, his ruler will expand
along with the space, so that the new “larger” distances will measure
the same size with HIS new “larger” ruler and so, I can’t detect the
expansion of space.”  I'M PRETTY SURE HE'S MISTAKEN,?  Why or why not?

Do these articles provide a satisfying answer to the question?

http://216.239.41.104/search?q=cache:j85aaFEHuboJ:itss.raytheon.com/cafe/qadir/q507.htm

http://math.ucr.edu/home/baez/physics/Relativity/GR/expanding_universe.html

Well of course, if everything did expand equally with the overall
expansion of the universe, we wouldn't be able to detect it, and this
conversation wouldn't be taking place. ;-)  People often do ask how
space can be expanding, while all the objects within can remain
unstretched. The answer is that all the discrete objects we see are
bodies of atoms, molecules, etc., which are held together by their own
internal forces. These forces are, at the small scale of the elements
themselves, vastly stronger (many trillions of times stronger) than
the tendency to be carried along with the expansion of space. Even the
internal gravitational cohesion of a large galaxy is greater than the
dragging effect of spatial expansion. It only gets stronger than
internal forces on a scale significantly larger than several million
light years.

-Mark Martin